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  • 1
    ISSN: 1075-2617
    Keywords: conformational analysis ; NMR spectroscopy ; X-ray diffraction ; peptide-based taste ligands ; artificial sweeteners ; computer simulations ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A dipeptide taste ligand L-aspartyl-D-2-aminobutyric acid-(S)-α-ethylbenzylamide was found to be about 2000 times more potent than sucrose. To investigate the molecular basis of its potent sweet taste, we carried out conformational analysis of this molecule and several related analogues by NMR spectroscopy, computer simulations and X-ray crystallographic studies. The results of the studies support our earlier model that an ‘L’-shape molecular array is essential for eliciting sweet taste. In addition, we have identified an aromatic group located between the stem and the base of the ‘L-shape’, which is responsible for enhancement of sweetness potency. In this study, we also assessed the optimal size of the essential hydrophobic group (X) and the effects of the chirality of the second residue toward taste. ©1997 European Peptide Society and John Wiley & Sons, Ltd.
    Additional Material: 11 Ill.
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  • 2
    ISSN: 1075-2617
    Keywords: β-bend ; cyclic amino acid ; 310-helix ; peptide conformation ; X-ray diffraction ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A series of N- and C-protected, monodispersed homo-oligopeptides (to the dodecamer level) from the small-ring alicyclic Cα,α-dialkylated glycine 1-aminocyclobutane-1-carboxylic acid (Ac4c) and two Ala/Ac4c tripeptides were synthesized by solution methods and fully characterized. The conformational preferences of all the model peptides were determined in deuterochloroform solution by FT-IR absorption and 1H-NMR. The molecular structures of the amino acid derivatives Z-Ac4c-OH and Z2-Ac4c-OH, the tripeptides Z-(Ac4c)3-OtBu, Z-Ac4c-(L-Ala)2-OMe and Z-L-Ala-Ac4c-L-Ala-OMe, and the tetrapeptide Z-(Ac4c)4-OtBu were determined in the crystal state by X-ray diffraction. The average geometry of the cyclobutyl moiety of the Ac4c residue was assessed and the τ(N-Cα-C′) bond angle was found to be significantly expanded from the regular tetrahedral value. The conformational data are strongly in favour of the conclusion that the Ac4c residue is an effective β-turn and helix former. A comparison with the structural propensities of α-aminoisobutyric acid, the prototype of Cα,α-dialkylated glycines, and the other extensively investigated members of the family of 1-aminocycloalkane-1-carboxylic acids (Acnc, with n=3, 5-8) is made and the implications for the use of the Ac4c residue in conformationally constrained peptide analogues are briefly examined. © 1997 European Peptide Society and John Wiley & Sons, Ltd
    Additional Material: 8 Ill.
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  • 3
    ISSN: 1075-2617
    Keywords: β-turn ; cyclic amino acid ; 310-helix ; peptide conformation ; X-ray diffraction ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A series of N- and C-protected, monodispersed homo-oligopeptides (to the pentamer level) from the cycloaliphatic Cα,α,-dialkylated glycine 1-aminocyclononane-1-carboxylic acid (Ac9c) and two Ala/Ac9c tripeptides have been synthesized by solution methods and fully characterized. The conformational preferences of all the model peptides were determined in deuterochloroform solution by FT-IR absorption and 1H-NMR. The molecular structures of the amino acid derivatives mClAc-Ac9c-OH and Z-Ac9c-OtBu, the dipeptide pBrBz-(Ac9c)2-OtBu, the tetrapeptide Z-(Ac9c)4-OtBu, and the pentapeptide Z-( Ac9c)5-OtBu were determined in the crystal state by X-ray diffraction. Based on this information, the average geometry and the preferred conformation for the cyclononyl moiety of the Ac9c residue have been assessed. The backbone conformational data are strongly in favour of the conclusion that the Ac9c residue is a strong β-turn and helix former. A comparison with the structural propensity of α-aminoisobutyric acid, the prototype of Cα,α-dialkylated glycines, and the other extensively investigated members of the family of 1-aminocycloalkane-1-carboxylic acids (Acnc, with n=3-8) is made and the implications for the use of the Ac9c residue in conformationally constrained analogues of bioactive peptides are briefly examined. © 1997 European Peptide Society and John Wiley & Sons, Ltd.J. Pep. Sci. 3: 367-382No. of Figures: 10. No. of Tables: 6. No. of References: 62
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
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